Hypodermic tubing, dental broaches, and the like



Oct. 7, 1947. s. J. EVERETT 2,428,518

HYPODEHMIC TUBING, DENTAL BROACHES AND THE LIKE Filed Dec. 31, 1943Inventor 54 40: James VIRA'77',

By QM R gmtlorney Patented Oct. 7, 1947 HYPODERMIC TUBING, DENTALBROACHES, AND THE LIKE Samuel James Everett, Thornton Heath, EnglandApplication December 31, 1943, Serial No. 516,573

In Great Britain January 1, 1943 This invention relates to line metalarticles,

such as hypodermic needles, dental breaches and the like, and to amethod of manufacturing the same.

needle embodying the invention,

7 Claims. (Cl. 128221) not embodying the invention.

Figure 2B is a similar view showing a fracture One of-the disadvantagesof articles of this resulting from severe bending stresses in a, needletype is that having relatively fine diameters and embodying theinvention. being subjected to'bending stresses during use, g re 3 is adiagrammatic view of p t f a they are sometimes broken, thus causinginjury broken dental tool embodying the invention, and to the patient..The broken 'off pieces frequently i ures 4 and 5 a e cross-Sections,respfictively. become lodged in body tissueand being small are show gdiag y, billets used in t sometimes lost or difllcult of extraction,manufacture of further implements in accord- In accordance with thepresent invention such ance with the invention. articles are providedwith'a fibrous structure with Fi ure 1 illustrat s aphi ally the a p atn the fibers being disposed predominantly transof the invention tohypodermic needles. In thev versely to the radius on which the bendingtak figure a portion of such a needle I is illustrated in place; crosssection. The article is constructed prefer- Where the article forexample is a hypodermic ably of austenitic nickel-chromium steel and forneedle, the crystalline structure of the needle is purposes ofillustration the fibrous arrangement analogous to cane or bamboo with thfibrous of the crystalline structure of the material is instructurebeing disposed predominantly longitudicated in dash lines 1 dinally ofthe needle. A hypodermic nee so It will be noted that the fibrousarrangement is constructed resists breaking into two separatepredominantly longitudinally of the needle which and distinct portionsto a greater degree, Severe revents the needle from breaking trans ersebending of the article may cause" the needle to into tW Sepa ate pieceswhen subjected to bendsplit longitudinally, but breakage into twosepaing stresses. 4 rate parts is most difilcult. Figure 2A illustratesdiagrammatically what In the example of the hypodermi needle, if happenswhen a needle 2, as hitherto manufacthe needle is bent severely durinusage, th tured, snaps as a result of severe bending. The fibers on theouter radius may break but th metal at the outside of the bend parts at2a while inner fibers split from the adjacent fibers so that at 2b er ia sharp k k- Further bending the inner fibers bendon an easy orsubstantial W ll cause the n le to n p complet ly into tWO radius suchthatfthey remain intact. There is. Sep P rts. therefore, substantiallyno risk of the needle Figure 2B, on the other hand, shows whathapsnapping into two separate and distinct parts. Pens when a eed eConstructed acCOrding t th If the needle then breaks while in bodytissue, invention snaps as a result of severe bending. there is no riskof the broken part becoming lost Again the metal at the outside of thebend snaps in the body. at 2a but the metal then splits longitudinallyIt is a general object of the invention to proat 20 'so that the metalat the inside of the bend vide. fine metal articles such as hypodermicneeis gently curved at 2d. Further bending will not dles, tubing, dentalbroaches, surgical instru- 40 substantially increase the radiusof'curvature at ments, and the like, which possess this charac- 2d andthere is little risk of the metal breaking teristic. I at M so thatthere is little risk of a part of the The invention has foranotherobject the proneedle being left in the patients body tissue. visionoffine metal articles of-austenitic nickel- Thisproperty is due to thecane-like structure, of chromium steeL'the crystalline structureof whichthe metal fromwhich the needle is made. is disposed predominantly in onedirection, pref- Figure 3 is a diagrammatic section through a erably atright angles to the radius onwhich the portion of a dental breach 3according to the inbending takes place. vention, the arrangement of thefibrous crystal- These and other objects of the invention will linestructure being indicated by the dash lines become more apparent fromthe following debearing the reference-numeral 4. Whenthe scription-andclaims when read in conjunction broach is bent to such an extent thatthefibers with the accompa'nyingdrawings inwhich: at the outside of thebend snap at 3a, longitudinal Figure 1 is a diagrammatic representationof splitting takes place at 30 so that the fibers on the a section takenthrough the end of a hypodermic inside of the bend are on a. long radiusand the parts of the breach remain held together.

'may be heated for a somewhat longer time at 900 C., or heated for ashorter period at 1150 0., this being normal softening. The grain sizecan be controlled by the usual well known practice of quenching in oilor water.

The temperatures to which the final heating is carried in order toremove the stress or strain within the material may be varied but it isdesired that this should be accomplished without destroying the fibrousstructure which the material has at that time acquired. Thus, thearticle may be heated for a fairly long period at a temperature as lowas 350 0., or for a shorter period as high as 475 C. In general, it maybe said that experiments show that for most requirements the temperatureshould be about 400 C. for about two seconds for'every one thousandth ofan inch cross-sectional dimension, as for example, wall thickness of atube or the diameter of a breach. If the heating is done at too low atemperature or too quickly, the required stability of the crystallinemetallic structure is not obtained.

The type of austenitic nickel-chromium steel employed in making articlesin accordance with the invention may vary within limits. However, thefollowing is an example of the type of steel which can be employedadvantageously: Firths D. D. Q. steel containing 12% nickel and 12%chromium, the remainder being iron with traces of carbon and silicon.The steel should possess a high degree of resiliency and spring temperand great strength. Steels containing 18% nickel and 8% chromium can becold worked to produce the required structure but are not sosatisfactory in regard to their mechanical properties.

In producing fine tubing such as is employed in making hypodermicneedles the following process is given by way of example: A billet ofaustenitic nickel-chromium steel is first drilled and by normal drawingprocess is then, reduced until it has an outside diameter ofapproximately actually made about 0.008 inch smaller than the bore. Thetube can then be cold drawn to 20 gauge, that is, 0.036 inch outsidediameter. It is then straightened and heat treated at 400 C. for fifteenminutes to soften the brass mandrel and improve the structure of thesteel. Finally, the tubing is divided into convenient lengths with out,however, cutting the mandrel and the lengths are then drawn off themandrel. The resulting lengths of tubing are found to have thelongitudinal fibrous structure required. A similar method may beemployed for the manufacture of dental broaches and similar fine steelinstruments which are subjected to stresses approaching their ulti= matestrength, thereby eliminating the ever-present danger of losing aportion of the instrument I in the tissue of the body or cavity which isbeing operated upon.

It is. of course, a fact that the instrument when broken cannot alwaysbe pulled directly from the cavity or tissue, but the strong adherenceof the broken part to the shank or remainder of the instrument enablesthe surgeon to make an incision in the correct place so that the partscan be successfully withdrawn.

In a modification of the aforesaid example, the initial billet, whichmay be half an inch to la inch in diameter, may comprise a sheath 8 ofaustenitic nickel-chromium steel over a tube 9 of stainless carbonsteel, as shown in Figure 4. Heat treating at 1000" 0., followed by airquenching softens the outer tube and hardens the inner one. An internalcorrosion resisting lining in may be provided by providing inside theinitial billet, a layer of nickel-silver, silver or nickelchromiumstainless steel. After the heat treatment, the composite billet is ofcourse subjected to the extreme reduction in cross-section withoutfurther re-heating, as in the preceding example, to provide theaustenitic nickel-chromium steel with the required fibrous or cane-likestructure and thereby impart the required mechanical properties. To addto the fibrous structure high tensile wires II are embedded in the softexternal sheath, the wires becoming integral with the tube wall duringthe extensive drawing oper ations. The final cane-like structure mayalso be enhanced by milling longitudinal slots in the initial billet.

As a variation of the methods just described, the fibrous structure ofthe tubing may be enhanced by building up the initial tubular billetsfrom segments 92 (Figure 5) brazed together at their edges, the brazedjoints i3 being not quite so strong as the segments themselves. Ifdesired the segments can be composed of different metals.,

,the internal strain.

It will be understood that some changes may be made in the invention andthat the description given in the accompanying illustrations are only tobe considered as examples.

I claim:

1. An elongated surgical member of substantially reduced cross sectionand which is normally subjected during use to bending strains, saidmember being of austenitic nickel-chromium steel, the crystallinestructure'of the steel inthe finished article being comprised ofparallel elongated fibers disposed predominantly parallel to thelongitudinal axis of saidelongated member.

2. A surgical device or the like comprising an elongated thin steel bodyof cane-like fibrous structure comprised of longitudinally arrangedelongated crystals, said longitudinallynrrang'ed elongated crystalsbeing disposed substantially parallel to the longitudinal axis of saidelongated steel body. 1

3. A surgical device or the like comprising an elongated austeniticnickel-chromium steel member of materially reduced cross section, saidmember having a predominantly longitudinal crystalline structure, readyto split longitudinally on bending.

4. A surgical device of austenitic nickel-chro- 5 mium steel, saiddevice being elongated and having a reduced cross sectional diametersubstansheath of austenitic nickel-chromium steel, renl5 dered cane-likein structure by cold elongation in the direction of the axis of theneedle.

7. A hypodermic needle comprising a tube of austenitic nickel-chromiumsteel rendered canelike in structure by elongation in the cold state inthe direction of the axis of said needle and a highly corrosionresistant layer on the inner surface of such tube.

SAMUEL JAMES REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 2,217,602 Smith Oct. 8, 1940 102,208,606 Smith July 23, 1940 7 2,041,778 Peters May 26, 1936 Re. 14,820Sallows Mar. 16, 1920 2,145,171 Giles Jan. 24, 1939 2,187,259 BarnhartJan. 16, 1940 2,217,602 Smith Oct. 8, 1940 145,217 Leiter Dec. 2, 1873-1,942,150 Rohn Jan. 2, 1934 OTHER REFERENCES 20 Metallurgy &Metallurgical Engineering Series,

The Structure of Metals, C. S. Barrett, pp. 446 to 448.

Transactions American Society for Metals, vol. 23, Jam-Dec. 1935, pp.400-404.

